✅Coasts Flashcards
(176 cards)
1
Q
Geomorphological processes - weathering
A
Mechanical - climate related (freeze thaw weathering)
Biological - breakdown by the action of vegetation and other costal organisms
Chemical - oxidation / hydration / hydrolysis / carbonation - co2 dissolved in rainwater makes a weal carbonic acid that reacts with limestone and chalk
2
Q
Geomorphological processes - mass movement
A
Large scale downward movement of rocks and material (sediment) that moves due to gravity.
3
Q
Geomorphological processes - erosion
A
Process by which earthen materials are worn away and transported by natural forces such as wind of water.
Similar to weathering but erosion does not involved the movement of sediment.
4
Q
Geomorphological processes - deposition
A
The laying down of sediment carried by wind, flowing water, sea or ice.
5
Q
Coastal processes - hydraulic action
A
Erosion
Wave pounding (sea action) the force of water on rocks
6
Q
Coastal processes - wave quarrying
A
Erosion
Breaking wave traps air in cracks in a cliff face, as the water pulls back, air is released under pressure which weakens the rock face overtime
7
Q
Coastal processes - corrasion / abrasion
A
Erosion
Sand, shingle and boulders picked up by the sea and hurled against a cliff
8
Q
Coastal processes - solution / corrasion
A
Where fresh water mixes with salt water, acidity may increase and carbon based rocks at the coast will be broken down
9
Q
Coastal processes - cavitation
A
Erosion
Compression of air in sea-facing joints as waves crash against cliffs can cause sea water to be severely compressed. As the wave recedes the pressure reduces and air comes out of solution in violent ‘fizzing’, enlarging fissures within joints.
10
Q
Coastal transport - solution
A
Dissolved material
11
Q
Coastal transport - attrition
A
When rocks carried by the sea knock against each other, breaking apart into smaller and rounder pieces.
12
Q
Coastal transport - traction
A
Large boulders roll along the seabed
13
Q
Coastal transport - suspension
A
Very small particles carried in the moving water
14
Q
Coastal transport - longshore / littoral drift
A
Waves approach the shore at an angle, swash moves material up the beach in the same direction as the wave, backwash moves the material back down the steepest gradient - usually perpendicular - where its picked up by the next incoming wave
15
Q
Mechanical weathering
A
Climate related
Eg. Freeze thaw weathering: pressure release of underlying rock - where overlying material is removed by erosion, weathering or mass movement.
16
Q
Coastal deposition - mass movement
A
General term for the movement of rock, soil or sediment down slopes under the force of gravity.
17
Q
Coastal deposition - runoff
A
Runoff occurs when there is more water than land can absorb. The excess liquid flows across the surface of the land and into nearby creeks, streams, or ponds.
18
Q
How does a cliff form?
A
Coastal erosion
Waves attack the base of the newly exposed rock faces. By hydraulic action and abrasion, and the other processes of coast erosion, the base of the cliff is undercut to form a wave-cut notch.
The rock face above the effects of wave action begins to overhang.
As waves continue erosional processes upon the base of the cliff, the size of the overhang increases until the weight of the rock above can no longer be supported and a section of the cliff collapses.
19
Q
How does a wave cut platform form?
A
Coastal erosion
The sea attacks the base of the cliff between the high and low tide marks.
Erosion processes of hydraulic action and abrasion, create a wave-cut notch.
Over time the notch increases in size and the upper cliff is unsupported, while weathering weakens the upper cliff.
These processes cause the cliff to collapse.
A wave-cut platform is the bedrock that is left behind as the cliff moves backwards.
The backwash carries the rubble towards the sea smoothing the wave-cut platform through abrasion.
20
Q
How does a cave form?
A
Coastal erosion
Initially, faults in the headland are eroded by hydraulic action and abrasion to create small caves.
The overvaluing rock in a cave my collapse, forming a blowhole. The blowhole spirts water when a wave enters at the base forcing sea spray and air out.
Marine erosion widens faults in the base of the headland, widening overtime to create a cave.
21
Q
How do arches form?
A
Coastal erosion
Initially, faults in the headland are eroded by hydraulic action and abrasion to create small caves.
The overvaluing rock in a cave my collapse, forming a blowhole. The blowhole spirts water when a wave enters at the base forcing sea spray and air out.
Marine erosion widens faults in the base of the headland, widening overtime to create a cave.
The cave will widen sue to both marine erosion and sub-aerial process, eroding through to the other side of the headland creating an arch.
22
Q
How does a stack form?
A
Initially, faults in the headland are eroded by hydraulic action and abrasion to create small caves.
The overvaluing rock in a cave my collapse, forming a blowhole. The blowhole spirts water when a wave enters at the base forcing sea spray and air out.
Marine erosion widens faults in the base of the headland, widening overtime to create a cave.
The cave will widen sue to both marine erosion and sub-aerial process, eroding through to the other side of the headland creating an arch.
The arch continues to widen until its unable to support itself, falling under its own weight through mass movement, leaving a stack as one side of the arch becomes detached from the mainland.
23
Q
Coastal transport - saltation
A
Small stones bounce along the seabed
24
Q
Biological weathering
A
Breakdown by the action of vegetation and other coastal organisms
25
Chemical weathering (4)
Oxidation - O2 dissolved in water reacts with some rock minerals (iron rich rocks)
Hydration - physical addition of water to minerals in rocks that makes them more susceptible to chemical weathering
Hydrolysis - mildly acidic water reacts with minerals
Carbonation - CO3 dissolved in rainwater makes a weak carbonic acid, which reacts with calcium carbonate in limestone and chalk
26
What are sub-aerial mass movements dependant on
Slope angle
Grain size
Temperature
Saturation
27
Sub-aerial mass movements - landslides
Cliffs made of softer rocks slip when lubricated by rainfall
28
Sub-aerial mass movements - rockfalls
Rocks undercut by the sea or sloped affected by mechanical weathering
29
Sub-aerial mass movements - mud flows
Heavy rain causes fine material to move downhill
30
Sub-aerial mass movements - rotational slip/slumping
Where soft material overlies resistant material and excessive lubrication takes place
31
Sub-aerial mass movements - soil creeping
Very slow movement of soil particles down slope
32
Sub-aerial mass movements - runoff
The moment of water across the hard surface, carrying debris
33
How does a beach form
Coastal deposition
Constructive waves (usually during summer months), deposition of material by low energy waves.
34
Swash aligned beaches
Wave crests approach perpendicular to coast so there is limited longshore drift.
Sediment doesn’t travel far along the beach.
Wave refraction may reduce the speed of high energy waves, leading to the formation of a shingle beach with larger sediment.
35
Drift aligned beaches
Waves approach at a significant angle, so longshore drift causes the sediment to travel far along the beach, which may lead to the formation of a spit at the end of a beach.
Generally larger sediment is found at the start of the beach and weathered sediment moves further down the beach through longshore drift, becoming smaller as it does, so the end of the beach is likely to contain smaller sediment.
36
Spit definition
Depositional feature
Long narrow strip of land formed by long shore drift, caused by a change in coastline direction.
37
How’s a spit formed?
The prevailing wind pushes constructive waves up the beach at an angle as the swash.
The waves then travel at a ninety degree angle back down the beach due to gravity as the backwash.
Sediment is pushed up and dragged back down the beach in this way through the process, longshore drift.
This process continues down the entire beach, leading to mass transportation of sediment, until the mainland ends. At this point, sediment is deposited and builds up causing an extension of the mainland out into the sea as a spit.
Spits can form a recurved hook as to secondary winds cause sediment deposition to occur at a different angle than previously. A salt marsh can form behind a spit if an estuary is present due to the mixing of fresh water, salt water and sediment.
38
Barrier beach definition
A barrier beach occurs when a beach or spit extends across a bay to join two headlands.
This traps water behind it leading to the formation of a brackish lagoon which is separated from the sea.
39
How does a barrier beach form?
Rising sea levels in the last glacial period, meltwater from glaciers deposit sediment in the coastal zone.
Longshore drift moves sediment along the coastline until there is a change in the coastline. A spit develops, usually in a bay and once the spit develops across the whole bay, a barrier beach forms.
Barrier beaches are unlikely to form in estuaries as the out coming force of freshwater will always keep part of the estuary clear.
Colonisation by vegetation can stabilise the barrier beach and trap further sediment keeping the barrier beach above sea even at high tide.
40
Tombolo definition
Bar or beach that connects the mainland to an offshore island and is formed due to wave refraction off the coastal island reducing wave velocity, leading to deposition of sediments.
They may be covered at high tide if they are low lying.
41
Tombolo formation - drift aligned
On drift aligned coastlines, when longshore drift builds a spit out from land until it contacts with an offshore island.
42
Tombolo formation - swash aligned
Wave refraction around both sides of the island.
This causes a collision of wave fronts on the landward side, cancelling each other out and producing a zone of still, calm water where deposition occurs, between the island and the coast.
Oppositional longshore currents may play a role, in which case the depositional feature is similar to a spit.
43
Offshore bar definition
An offshore region where sand is deposited, as the waves don’t have enough energy to carry the sediment to shore.
44
How does an offshore bar form?
They can be formed when the wave breaks early, instantly depositing its sediment as a loose-sediment offshore bar. Waves may pick up sediment from an offshore bar, which then provides an important sediment input into the coastal zone. They may also be formed as a result of backwash from destructive waves removing sediment from a beach. Offshore bars may absorb wave energy, reducing erosion in some areas.
45
Estuarine Mudflats and Salt marshes
Decomposition occurs in river estuaries due to the opposing flows of water causing the flow of water to cease and flocculation.
Flocculation - salt water and freshwater mix causing the small suspended particles to limp and form larger aggregates or flocs. They then settle to the bottom of the water (sedimentation).
46
Negative feedback loop coasts
Lessens any change thats occured.
Destructive waves from the storm lose their energy and excess sediment is deposited as an offshore bar.
The bar dissipates wave energy which protects the beach from further erosion.
Overtime the bar gets eroded instead of the beach.
Once the bar has gone to normal conditions and the system goes back to dynamic equilibrium.
47
How does sea level change
Short-term (day to day / minute to minute due to low tide and high tide, wind strength and wind direction or changes in atmospheric pressure)
Lower pressure - higher seas
Long term - formation of coastal landscapes
48
Isostatic sea level change
When the land rises or falls relative to the sea - LOCAL CHANGE
Can be caused through tectonic activity changing land shape - seen in 2004 Indian Ocean Earthquake
Can be caused trough Isostatic subsidence (glaciers weigh down the land beneath so the land subsides).
49
Eustatic sea level change
Affects sea level across the whole planet.
Can be due to thermal expansion / contraction or changes in glacial processes.
Thermal expansion - water expanding when sea gets warmer so volume of water rises = rising sea levels.
50
Emergent coastal landscape
Where land has been raised in relation to the coastline
Arches, stacks and stumps
Raised bleachers
51
Submergant coastal landforms
When the sea level rises or the coastline sinks in relation to the sea.
52
Rias
Submegent feature
formed when rising sea levels flood narrow winding inlets and river valleys. They are deeper at the mouth of the inlet, with the water depth decreasing further inland
Example - Kingsbridge Estuary, Devon
Example - Jacksons Harbour - Sydney Harbour, Australia
53
Fjord
Submergent feature
Rising sea levels flood deep glacial valleys to create natural inlets and harbours.
Example - Loch Long Scotland
54
Dalmatian coasts
Submergent feature
This type of coastline occurs when valleys running parallel to the coast become flooded as a result of sea level change. This leaves a series of narrow, long and rugged islands
55
How much has the sea level risen since 1880
235mm
56
effect of climate change on coasts
More Eustatic change
More submergent features due to rising sea levels
Population distribution change (environmental refugees)
Land decrease while population increasing
Loss of farmland
Cities, countries lost
57
Drift aligned vs Swash aligned beaches
Drift-aligned beaches form where longshore drift moves the sediment along the beach as waves approach at an oblique angle.
This will often culminate in a spit where the coastline changes direction.
Swash-aligned beaches form where the energy is low.
The waves are more parallel to the shore in swash-aligned environments so there is very little horizontal or lateral movement of sediment.
58
Name the 4 sources of energy in a coastal environment
1. Winds
2. Waves (constructive and destructive)
3. Currents
4. Tides
59
Describe wave formation
Winds move across the surface causing frictional drag which creates small ripples and waves. This leads to a circular orbital motion of water particles in the ocean.
As the seabed becomes more shallow near the coastline, the orbit becomes more elliptical, leading to more horizontal wave movement.
Wave height increases but wavelength and velocity both decrease.
This causes water to back up behind the wave until the wave breaks.
60
How does strength of wind affect wave energy?
Wind = air that moves from an area of high to low pressure.
The difference in pressure areas are caused by variations in surface heating by the sun. The larger the difference in pressure between 2 areas (pressure gradient) the stronger the winds.
As waves are caused by the wind, stronger winds = stronger waves.
61
How does duration of wind affect wave energy?
If winds active for longer periods of time = energy of the waves continues to build up.
62
How does size of fetch affect wave energy?
Fetch = distance over which the wind blows (unbroken).
The larger this is the more powerful the waves will be.
63
Constructive vs Destructive waves - formation
Constructive
- Formed by weather systems that operate in the open ocean.
- Form in sheltered bays.
Destructive
- Localised storm events with stronger winds operating closer to the coast.
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Constructive vs Destructive waves - wavelength
Constructive
- long wavelength.
Destructive
- short wavelength.
65
Constructive vs Destructive waves - frequency
Constructive
- 6-9 per minute (less)
Destructive
- 11-16 per minute (more)
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Constructive vs Destructive waves - characteristics
Constructive
- low waves, which surge up the beach
Destructive
- high waves, which plunge onto the beach
67
Constructive vs Destructive waves - swash characteristics
Constructive
- strong swash and weak backwash
Destructive
- weak swash and strong backwash
68
Constructive vs Destructive waves - effect on beach
Constructive
- occurs on gently sloped beaches
Destructive
- occurs on steeply sloped beaches
69
Tides as a key source of energy
Gravity = key source of energy and responsible for tides (4 a day).
The gravitational pull of the sun or moon change the water levels of the seas and oceans. The difference in height between the tides = tidal range.
Highest tide and lowest tide caused when the sun and moon are perpendicular to each-other.
70
Define neap tide
The water does not rise or fall to its usual heights.
When the sun and moon at at right angles to each other.
A high tide will be less high and a low tide will be less low, decreasing the difference between them.
71
Currents as a key source of energy
Rip currents - powerful underwater currents that occur close to the shoreline and the backwash is forced under the surface due to resistance from breaking waves. Can lead to outputs of sediment from a beach.
Riptides - ocean tide pulls water through a small area such as a bay or a lagoon.
72
High energy coastlines
Associated with more powerful waves, occur in areas where there is a large fetch.
Typically have rocky headlands and landforms and fairly frequent destructive waves.
Rate of erosion > rate of deposition.
73
Low energy coastlines
Associated with less powerful waves and occur in sheltered areas where there is a smaller fetch.
Constructive waves prevail as a result and there are often sandy areas - depositional landforms.
Rate of deposition > rate of erosion.
74
Define wave refraction
Process by which waves turn and lose energy around a headland on uneven coastlines. The wave energy is focused on the headlands making erosional features.
The energy is dissipated in the bays making features associated with lower energy environments such as beaches.
75
Negative feedback - beaches and waves
The presence of constructive waves = deposition on the beach = steeper beach profile.
Steeper beaches favour the formation of destructive waves.
Destructive waves erode the beach reducing the beach profile and leading to the formation of constructive waves.
Rebuilds the beach profile.
76
Define a sediment cell
Littoral cells - reaches of shoreline that encompass the intertidal and nearshore movement of sediment.
Can be considered a coastal sub-system.
Areas along the coastline and in the nearshore area where the movement of material is largely self-contained.
77
Define dynamic equilibrium
Maintence of balance in a natural system, despite it being in a constant state of change.
The system has a tendency to counteract any changed imposed on the system in order to achieve this balance.
78
Coastal inputs
Marine - waves / tides
Atmosphere - sun / air pressure / wind
Humans - pollution / sediment / defences
Natural - sediment
79
Coastal outputs
Ocean currents
Rip rides
Sediment transfers
Evaporation
80
Coastal stores / sinks
Beaches
Sand dunes
Spits
Bars / tombolos
Headlands / bays
Cliffs
Wave cut platforms / notches
Nearshore sediment
Caves / arches / stacks / slumps
Salt marshes
Tidal flats
Offshore bands and bars
81
Coastal transfers
Mass movement processes
Long shore drift
Weathering
Erosion
Transport
Deposition
82
Negative vs positive feedback
Negative - lessens any change which has occurred and brings the system back to normal.
Positive = exaggerates the change making the system more unstable and taking it away from dynamic equilibrium.
83
Negative feedback example
1. Destructive waves from a storm lose their energy and excess sediment is deposited as an offshore bar.
2. The bar dissipates the waves energy which protects the beach from further erosion.
3. Overtime the bar gets eroded instead of the beach.
4. Once the bar has hone normal conditions ensue and the system goes back to dynamic equilibrium.
84
Positive feedback example
1. People walking over sand dunes destroys vegetation growing there and causes erosion.
2. As the roots from the vegetation have been holding sand dunes together, damaging the vegetation makes the sane dunes more susceptible to erosion. This increases the rate of erosion.
3. Eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from the original state.
85
Sediment sources - rivers
Accounts for most of the sediment input, especially in high rainfall environments where significant river erosion occurs.
Sediment may be deposited in estuaries (salty areas where rivers flow into the sea).
86
Sediment sources - cliff erosion
Very important in areas with unconsolidated (uncompacted and therefore unstable) cliffs that are eroded easily.
Most erosion occurs during the winter months due to more frequent storms
87
Sediment sources - wind
The wind is a coastal energy source and can cause sand to be blown along or up a beach.
Sediment transport by winds may occur where there are sand dune which provide sediment inputs.
88
Sediment sources - glaciers
In some coastal systems such as in Antarctica, glaciers flow directly into the ocean depositing sediment that was stored in the ice.
This occurs when glaciers calve, a process where ice breaks off the glacier.
89
Sediment sources - offshore
Sediment is transferred to the coastal zone when waves, tides and currents erode offshore sediment sinks such as offshore bars. The sediment is transported onto the beach, helping to build up the beach.
Storm surges or tsunami waves may also transfer sediment into the coastal zone
90
Sediment sources - longshore drift
Sediment moved up along the beach due to prevailing winds which alter wave direction.
91
What effects sediment budgets
Human and natural variations - disrupt the state of equilibrium.
92
Define the littoral zone
Area of land between the cliffs or dunes on the coast and the offshore area thats beyond the influence of waves. Therefore it is covered by the sea at different points in time.
93
Why’s the littoral zone constantly changing?
Short term - tides and storm surges.
Long term - changes in sea level and human intervention.
94
Define plant succession
Vegetation succession is a plant community that changes over time. On coasts where there’s a supply of sediment and deposition occurs, pioneer plants begin to grow in bare mud and sand.
95
Describe sand dune succession
1. Embryo dunes are first colonised by pioneer plants.
2. These die and release nutrients into the sand, increasing the amount of vegetation able to grow in the dune by making the environment less harsh.
3. Embryo dunes and their pioneer plants alter the environmental conditions from harsh and salty, to an environment in which other plants can survive.
4. New species of plants can now colonise the area, which will change the environment progressively.
96
Why’s marram grass a good pioneer plant?
It is tough and flexible, so can cope when being blasted with sand.
It has adapted to reduce water loss through transpiration.
Their roots grow up to 3 metres deep and can tolerate temperatures of up to 60°C.
97
Salt marsh succession
1. Algal Stage - Gut weed & Blue green algae establish as they can grow on bare mud, which their roots help to bind together.
2. Pioneer Stage - Cord grass & Glasswort grow, their roots begin to stabilise the mud allowing the estuarine to grow.
3. Establishment Stage - Salt marsh grass & Sea asters grow, creating a carpet of vegetation and so the height of the salt marsh increases.
4. Stabilisation - Sea thrift, Scurvy grass & Sea lavender grow, and so salt rarely ever gets submerged beneath the marsh.
5. Climax vegetation - Rush, Sedge & Red fescue grass grow since the salt marsh is only submerged one or twice a year.
98
How does vegetation help stabilise coastal sediment?
Roots of plants bind soil together which helps to reduce erosion.
When completely submerged, plants provide a protective layer for the ground and so the
ground is less easily eroded.
Plants reduce the wind speed at the surface and so less wind erosion occurs.
99
Sand dune formation
Occur when prevailing winds blow sediment to the back and therefore the formation of dunes require large quantities of sand and a large tidal range.
This allows the sand to dry, so that it’s light enough to be picked up and carried by the wind to the back of the beach.
Frequent onshore winds are also necessary. The dunes develop as a process of vegetation succession.
100
Embryo dunes
Upper beach area where sand starts to accumulate around a small obstacle (driftwood, wooden peg, ridge of shingle)
101
Yellow dunes
As more sand accumulates and the dune growns, vegetation may develop on the upper and back dune surfaces, which stabilises the dune. The tallest of the dune succession
102
Grey dunes
Sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth
103
Dune slack
The water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of moisture-loving plants (e.g. willow grass)
104
Heath and woodland
Sandy soils develop as there is a greater nutrients content, allowing for less brackish plants to thrive. Trees will also grow (willow, birch, oak trees) with the coastal woodland becoming a natural windbreak to the mainland behind.
105
Estuarine, mudflat and salt marsh formation
Deposition occurs in river estuaries because when the flow of water from the river meet the incoming tides as the water flow ceases so no longer carries the suspension.
As most of the sediment is small it leads to mud build up which rises over water. Deposition also occurs as a result of flocculation. Pioneer plants colonise this area, leading to more sediment being trapped. This colonises the transition zone between high and low tide. A meadow is formed as sections of the salt marsh rise high above the tide levels leading to climax vegetation succession when the trees begin to colonise the area.
106
Stability of depositional landforms
Consist of un consolidated sediment making them vulnerable to change.
During major storms large amounts of sediment can be eroded or transported elsewhere, removing a landform from one region of the sediment cell.
Depositional landforms rely on a continuous supply of sediment to balance erosion, which may see some landforms change as their dynamic equilibrium shifts.
107
Sea level change
Short term - high tide / low tide / wind strength and direction / atmospheric.
Long term - leads to formation of various coastal landforms as a result of isostatic and eustatic changes.
108
Isostatic change
When the land rises or falls relative to the sea and is localised change. Often due to isostatic subsidence (glaciers weigh down the land beneath, and so the land subsides).
When the glaciers melted, this has lead to isostatic recovery and the coastline to rebound and rise again in the areas that were covered by ice. Scotland and the NW England are rising at around 1.5mm per year as they were previously covered by glaciers, but this has caused the land in the SE to subside around 1mm a year.
Tectonic activity can also cause land subsidence.
109
Eustatic change
Sea level change across the whole plant.
Can be due to thermal expansion / contraction or changes in glacial effects.
Last ice age - sea levels were over 100m lower than currently as the water was stored in large ice caps as the majority of precipitation fell as snow. When the ice caps melted= rising sea levels.
As a result of global warming, both processes are acting to increase sea levels with the IPCC predicting sea level increases for 0.3m - 1.0m by 2100. In Miami, they are currently facing significant problems, with much of the coastal strip flooding regularly during high tides as a result of rising sea levels.
110
Contemporary sea level change
Sea levels have risen from 120m since 20,000 years ago. This has slowed in the last 8,000 years.
Since 1880 (industrial revolution) sea levels have risen by 235mm.
IPCC predict 0.3-1m rise by 2100.
111
Holderness coastline - what physical factors work along this coastline
Weather - winter storms = stronger waves and high sea surges = intensifies the sub-aerial processes. The saturated cliffs suffer increased run off due to mass movement.
Waves - NE coast = dominant waves + large fetch / destructive waves = erode beaches and attack the foot of the cliffs. Tides near Humber Estuary allow sediments to collect = forming spits, mudflats and sand dunes near spurn head.
Geology = 2 main rock types are chalk and boulder clay, chalk is more resistant (Flamborough Head) and boulder clay more easily eroded (sweeping bay of Holderness) - differential erosion rates = unique coastline shape.
112
Holderness coastline - what features / processes make this coastline so distinctive (3)
1. Flamborough Head (headland made of chalk).
2. Retreating clay cliffs of the Holderness Bay.
3. 6km spit at Spurn Point.
113
Holderness coastline - Flamborough head
Resistant chalk headland which illustrates how wave erosion can produce classic arch, stack and wave cut platform features.
114
Holderness coastline - Holderness Cliffs
Mappleton is a good example – more easily eroded boulder clay class facing the combined effects of the sea (cliff-foot) erosion and land (cliff face) processes.
Waves and longshore drift awesome moving materials South.
115
Holderness coastline - Humber Estuary
Has helped wind, tides and river processes to develop ecosystems of dunes, mudflats and salt marshes.
116
Holderness coastline - spurn head
Settlements brought here by longshore drift are deposited where the winds, waves on the river esther I have created a large bit fragile recurred spit. 
117
Flocculation
Process by which when fresh water and salty water mix the small suspended particles group together and aggregate (making deposition more likely).
118
Sediment budgets
Use data inputs, outputs, stores and transfers to assess the gains and losses of sediment within a sediment cell. In principle a system will operate in a state of dynamic equilibrium where inputs and outputs of sediment are the same.
Human actions and natural variation can disrupt the system and its state of equilibrium.
119
Short term factors that affect the littoral zone
Tides and storm surges
120
Long term factor is that affect littoral zone
Changes in sea level and human intervention
121
Shore / shoreline
Boundary between sea and the land
122
Offshore
Area beyond the influence of waves
123
Onshore
Area of land not covered by the sea, but very close to it
124
Mechanical weathering - salt crystallisation
As seawater evaporates salts left behind. Salt crystals grow overtime excreting pressure onto the rock which forces the cracks to widen. Salt can also corrode iron containing material due to chemical reactions.
125
Mechanical weathering - freeze-thaw (frost shattering)
Water enters cracks in the rock then it freezes and expands by 10% which increases pressure on the rock, causing more cracks to develop. Overtime these cracks grow weakening the cliff.
126
Mechanical seating - wetting + drying
Rocks such as clay expand when wet then contract again when dry. The frequent cycles of wetting and drying at the coast can cause these rocks and cliffs to break up.
127
Positive feedback (weathering)
If the rate of removal of weathered rock from the base of the cliff is higher than the rate of weathering, then this promotes further wreathing as it increases the area of exposed rock so more erosion. More eroded materials able to become part of the abrasion and saltation process.
128
Negative feedback (weathering)
Of the rate of movement of the weathered rock is slower than the rate of weathering this will lead to a build up a debris at cliff base. Reduced the cliff exposure therefore reduced rate of weathering.
129
Chemical weathering - carbonation
Rainwater absorbs CO2 from the air to make weak carbonic acid that then reacts with CaCO3 in rocks to make CaCO2 (bicarbonate) which can then be easily dissolved. Acid reacts with limestone to make CaCO2.
130
Chemical weathering - oxidation
When minerals become exposed to the air through cracks and tissues, the mineral will become oxidised.
131
What’s the type of mass movement dependent on
Cliff ‘ close angle
Rock type
Rock structure
Vegetation
Saturation of the ground
Presence of weathering
132
Mass movement - soil creep
Slowest but most continues form of mass movement involving the movement of soil particles down hill.
Particles rise and fall due to wetting and freezing and in a similar way to LSD, this causes soil to move down slope.
Leads to formation of shallow terracettes.
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Mass movement - solifluction
Occurs mainly in tundra areas where the land is frozen (periglacial). As the top layers thaw during the summer (but lower layers still stay frozen due to permafrost) the surface layers flow over the frozen layers.
Forms solifluction lobes.
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Mass movement - mudflows
An increase in water soil content can reduce friction, leading to earth and mud to fow over underlying bedrock, or slippery materials such as clay.
Water can get trapped within the rock increasing the pore pressure therefore weakens the rock.
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Mass movements - rockfall
Occurs on sloped cliffs when exposed to mechanical weathering.
Leads to scree (rock fragments) building up at the base of the slope. Scree is a temporal store which acts as an input to the coastal zone.
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Mass movements - landslide
Heavy rainfall leads to water between joints and bedding planes in cliffs (parallels to cliff face) which can reduce friction and lead to landslide. It occurs when a block of intact rock moves down the cliff face very quickly along a flat slope.
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Mass movement - land slip or slump
Slope if curved, so often occur in weak and un-consolidated clay and sand areas.
A build up in pore water pressure causes the land to collapse under its own weight.
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Mass movement - runoff
Water in the form of overland flow may erode the cliff face and coastal area or pick up sediment that teh enters the littoral zone.
When transported as a suspension it may also be responsible for increasing pollution in coastal areas if it picks up waste or excess chemicals.
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How’s development of steep cliffs favoured?
Most common where the rock is strong and fairly resistant to erosion.
Sedimentary rocks that have vertical strata are also more resistant to erosion, creating steep cliffs.
An absence of a beach, long fetch and high energy waves also promote steep cliff development.
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How’s development of gentle cliffs favoured?
Found in areas with weaker rock which are less resistant to erosion and prone to slumming.
Low energy waves and a short fetch will lead to formation of a scree mound at the base of the cliff reducing the overall cliff angle.
A large beach would also reduce wave energy and prevent the development of steep cliffs by reducing erosion rates. Most commonly found in low energy environments.
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Rate of retreat
Dependant on the relative importance of marine factors (fetch, beach, wave energy) and terrestrial factors (sub aerial processes, geology, rock strength).
The cliffs most likely to retreat are those made of un consolidated rocks and sands.
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Berms (beaches)
Ridges which mark where the high tide line is at different times of the year, and as a result there may be several berms on the beach.
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Cusps (beaches)
Small curved dips in the beach where the swash comes in and are slightly lower than the rest of the beach.
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Runnells (beaches)
Smaller ridges often found in smooth wet sand towards the sea.
Caused by tides.
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How does vegetation stabilise a coastal environment
Roots bind soil together which reduces erosion.
When completely submerged, plants provide a protective layer for the ground so is less easily eroded.
Plants reduce the wind speed at the surface and so less wind erosion occurs.
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Dalmatian coastlines
Valleys running parallel to the coast become flooded as a result of sea level change.
Leaves a series of narrow, long and rugged islands - Croatia.
(May also be referred to as Pacific Coasts)
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Coastalisation
Process by which the coast is being developed and people are moving to the coast, increasing the number of people at risk from marine related environmental activity.
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Define a storm surge
Result of low pressure created by large weather events such as tropical storms. It raises the sea level, therefore poses a significant flooding risk as it has the potential to inundate flood defences, making other impacts of a tropical storm more potent.
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How’s a storm surge exacerbated
Removing natural vegetation - mangrove forests dissipate wave energy and keep up with global sea level raises up to 8x the current rate.
Global warming - as surface of oceans get warmer its predicted that the frequency and intensity of storms will increase (in turn increases storm surge).
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Consequences of coastal hazards to communities
Some areas of the coast may have significantly decreased house and land prices leading to economic loss for home owners and local coastal economic. In UK many insurers dont produce home insurance to people living along coastlines that are at extreme risk of erosion or storm surges.
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Storm surge damage to Spurn Head
Storm surges can damage the environment by destroying plant successions and damaging many coastal landforms.
Depositional landforms, due to their unconsolidated nature can be partially destroyed.
For example 2013, spit at spurn head.
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Coasts and population distribution
Globally more than 1 billion people live on coasts and are at risks of coastal flooding.
50% of the worlds population currently live within 60km of the coasts.
75% of all the worlds largest cities are coastal.
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Environmental refugees
As strom surges and erosion along some coastlines are predicted to increase, so too is the volume of environmental refugees.
People may lose their homes, way of life and culture as a result of being forces to migrate due to rising sea levels.
In low lying counties such as Bangladesh many people have already been forced to migrate.
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Define hard engineering
Traditional and involved man made structures that aim to prevent erosion.
They’re often very effective at at preventing erosion at the desired location but may have effects down drift and are very costly (econ and env - concrete).
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Offshore breakwater
HARD
Rock barrier which forces waves to break before reaching the shore.
Good = effective at reducing waves energy
Bad = visually unappealing / can interfere with LSD / navigation hazard for boats
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Groynes
HARD
Timber or rock protrusions that trap sediment from LSD.
Good = builds up beach, protecting cliff and increasing tourist potential / cost effective
Bad = visually unappealing / deprives areas down drift of sediment and causes erosion
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Sea walls
HARD
Concrete structures that absorb and reflect wave energy, with curved surface.
Good = effective erosion prevention / promenade has tourism benefits
Bad = visually unappealing/ expensive to construct and maintain / wave energy reflected somewhere else which impacts erosion rates elsewhere
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Rip Rap (rock armour)
HARD
Large rocks that reduce wave energy but allow water to flow though.
Good = cost effective
Bad = rocks are sources from elsewhere so don’t fit with local geology / potential hazard if climbed upon
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Revetments
HARD
Wooden or concrete ramps that help absorb wave energy.
Good = cost effective
Bad = visually unappealing/ constant maintenance- additional costs
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Soft engineering
Aims to work with complement the physical environment by using natural methods of coastal defence.
They’re useful for protecting agains sea-level change as well as coastal erosion.
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Beach nourishment
SOFT
Sediment taken from offshore sources to build up the existing beach.
Good = builds up beach protecting cliff / increasing tourist potential
Bad = needs constant maintenance / dredging may have consequences on local habitats
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Cliff regrading and drainage
SOFT
Reduces the angle of the cliff to help stabilise it. A steeper cliff would be more likely to collapse.
Good = cost effective
Bad = cliff may collapse suddenly as the cliff is drier leading to rock falls which pose a hazard / may look unnatural
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Dune stabilisation
SOFT
Marram grass planted. The roots help bind the dunes, protecting the land behind.
Good = cost effective / creates important wildlife habitat
Bad = planting is time consuming
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Marsh creation
SOFT
Type of managed retreat allowing low-lying areas to flood.
Good = creates an important wildlife habitat
Bad = farmed lose land and may need compensation as a result
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Cost Benefit Analysis (CBA)
Carried out before any form of coastal management takes place.
The expected cost of construction, demolition, maintenance of a coastal management plan is compared to the expected benefits.
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Examples of sustainable coastal management
1. Managing natural resources like fish, water, farm land to ensure long term productivity.
2. Ensuring there are new jobs for people who may face unemployment as a result of protection measures.
3. Educating communities about the need to adapt and how to protect the coastline for further generations.
4. Monitoring coastal changes and then using adaptation or mitigation as a response to the observed changes.
5. Ensure everyone is considered when changes are proposed then adopted.
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Integrated coastal zone management (ICZM)
Large sections of coastline (often sediment cells) are managed with 1 strategy.
Management occurs between different political boundaries, which is both beneficial and problematic as decision making is likely to be a longer process.
In UK - different couples work together to manage coasts.
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What does the ICZM recognise
1. Importance of coasts for peoples livelihoods
2. Coastal management must be sustainable whereby economic development is important but not prioritised over protection of the coastal environment.
3. Involves all stakeholders plan for the long term and try to work with natural processes and not against them.
4. Sediment eroded in 1 location may form a protective beach elsewhere and therefore a decision to protect 1 coastal community may not outweigh the disadvantages of exposing another community to increased erosion.
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In 2013 the EU…
Adopted a new initiative which promotes the use of the ICZM strategy across all Europe’s coastlines, which recognised the benefits of the ICZM strategy.
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Shoreline management plans (4)
1. Hold the line
2. Managed retreat
3. Advance the line
4. No active intervention
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Hold the line
Defences are used to maintain the current position of the shoreline
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Managed retreat
Defences and engineering techniques are used to allow the coastline to be advanced inland and create its own natural defences such as salt marshes.
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Advance the line
Defences are built to try and move the shoreline seawards, potentially to protect an important population centre or tourist amenity.
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No active intervention
Coastline exposed to natural processes
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What different factors are considered when choosing a management option
Economic value of assets that could be protected. A known area of gas reserves may be protected, though a caravan may not be.
Technical feasibility of engineering solutions. A sea wall may nit be possible for a certain location.
Ecological and cultural value of the land. It may be desirable to protect historic areas and SSSI’s.
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Impact of coastal managent on sediment cells
Installing a sea wall would reflect wave energy down-drift increasing wave energy and erosion elsewhere on the coastline.
Less erosion occurs in these areas with the sea wall so less sediment in the areas with increased wave energy,
Less sediment reduces the beach size and the cliff is more exposed to erosion from higher energy waves.
Building groynes has the same affect on down drift areas as LSD can no longer transport sediment away from stretch of coastline.
